While I was co-teaching an introductory course in musical acoustics a few years ago, our class investigated several pieces of equipment designed for audio purposes. One piece of such equipment was a pair of noise-canceling headphones. Our students were curious as to how these devices were in eliminating background noise and whether they indeed block low-frequency sounds as advertised.

They say that there is no such thing as a stupid question. In a pedagogically pure sense, that's probably true. But some questions do seem to flirt dangerously close to being really quite ridiculous. One such question might well be, “How many dimensions of space are there?” I mean, it's pretty obvious that there are three: left/right, up/down, and forward/backward. No matter how you express an object's coordinate, be it Cartesian, spherical, cylindrical, or something exotic, it's eminently clear that we live in a three-dimensional universe.

Today, almost all introductory physicstextbooks include standardized “rules” on how to find the number of significant figures in a calculated value.1–6 And yet, 30 years ago these rules were almost nonexistent. Whyhave we increased the role of significant figures in introductory classes, and should we continue this trend? A look back at the evolution of significant figures over the last 300 years, from Newton to Millikan to modern authors, sheds some light on their purpose moving forward. While there is much discussion for7,8 and against9,10 their use, especially in chemistry, a review of earlier versions of the rules suggests that we have lost some items of value, most notably, a significant figure rule for angles. In addition, we have lost the emphasis that the significant figure rules were designed to calculate an approximate (not exact) precision. Now that the significant figure rules are ingrained into our introductory physics sequence, we would be wise to reiterate that these are just general “rules of thumb.”

In April 1820, Hans Christian Ørsted noticed that the needle of a nearby compass deflected briefly from magnetic north each time the electric current of the battery he was using for an unrelated experiment was turned on or off. Upon further investigation, he showed that an electric current flowing through a wire produces a magnetic field. In 1831 Michael Faraday and Joseph Henry separately expanded on Ørsted's discovery by showing that a changing magnetic field produces an electric current. Heinrich Lenz found in 1833 that an induced current has the opposite direction from the electromagnetic force that produced it. This paper describes an experiment that can help students to develop an understanding of Faraday's law and Lenz's law by studying the emf generated as a magnet drops through a set of coils having increasing numbers of turns.

With the increased availability of modern technology and handheld probeware for classrooms, the iPad1 and the Video Physics2 application developed by Vernier are used to capture and analyze the motion of an ice hockey puck within secondary-level physics education. Students collect, analyze, and generate digital modes of representation of physics phenomena using modern technologies to complement theoretical plots. This activity acknowledges hockey players' implicit understanding of the launch angle and initial velocity of a saucer pass as basic projectile motion while engaging students in authentic physics-based problem solving.

As part of the new education initiatives of the Acoustical Society of America (ASA), an activity kit for teachers that includes a variety of lessons addressing acoustics1 for a range of students (K-12) has been created. The “Sound and Music Activity Kit” is free to K-12 teachers. It includes materials sufficient to teach a class of 30 students plus a USB thumb drive containing 47 research-based, interactive, student-tested lessons, laboratory exercises, several assessments, and video clips of a class using the materials. ASA has also partnered with both the Optical Society of America (OSA) and the American Association of Physics Teachers. AAPT Physics Teaching Resource Agents (PTRA) have reviewed the lessons along with members of the ASA Teacher Activity Kit Committee. Topics include basic learning goals for teaching the physics of sound with examples and applications relating to medical imaging,animalbioacoustics, physical and psychological acoustics,speech, audiology, and architectural acoustics.

We have just completed the data collection for our 2012–13 Nationwide Survey of High SchoolPhysics and expect to have results to report in the spring. In the interim, we will take a look at physics in two-year colleges (TYCs). In 2007, we surveyed undergraduate seniors in degree-granting physics departments, and we asked these students if they had begun the post-secondary career at a TYC. Nine percent of the physicsundergraduate seniors in 2007 had started their college education at a TYC, and these students differ significantly from those who did not start at a TYC. The two graphs at right depict the high schoolphysics experience for these two groups of students. More than one-fourth of those who started at a TYC did not take physics in high school, and only 18% took AP physics. The 6% of those who did not start at a TYC and did not take physics is consistent with the 5% of high school seniors who attend a school where physics is not offered. Their apparent difference of interest in physics in high school is also evident from their knowledge about AP physics offerings: 25% of those who started at a TYC did not know if AP physics was offered at their high school versus only 5% of those who did not start at a TYC. Since their high schoolphysics experiences were so different, it is likely that something happened in their physics courses at the TYC that captured these students' interest in physics.

The study of electricity and magnetism is fundamental to all first-year physics courses. Developing simple electricity laboratory experiences that are open ended and inquiry based can be difficult. We wished to create a lab experiment where the students have some control over the experimental design,data analysis is required, and students investigate the concept of resistivity as found in Halliday Resnick, and Walker.1 This experiment uses modeling clay or Play-Doh™ to demonstrate the properties of ohmic materials and resistivity. We were familiar with the paper “Resistance Measurements on Play-Doh™” by Jones2 and we have worked to more accurately explain the physics of the experiment. We have also further developed the experiment to better understand how the resistivity of Play-Doh changes with time. This lab is an exciting, fun experiment that connects a new concept with a familiar childhood toy.

In the popular press, diagrams showing the evolution of the universe begin with a great jump in size labeled “inflation.” Can we explain the basic ideas behind inflation to our students who have taken our introductory physics course? Probably not. In our standard introductory physics courses, even those with special relativity, something is missing. We do not talk about how space behaves, and that is a key component in modern astronomy. This is the first of four papers dealing with the behavior of space. They focus on basic cosmology and a discussion of inflation, building on the ideas and experiments covered in introductory physics.

The Frahm resonance principle, in which resonating reeds indicate the frequency of mechanical or electrical oscillations, is a hardy perennial. In this note we will give some history, show some original apparatus, and show how it may be reproduced with relatively little effort.

At our university, students in introductory physics classes perform a laboratory exercise to measure the range of a projectile fired at an assigned angle. A set of photogates is used to determine the initial velocity of the projectile (the launch velocity). We noticed a systematic deviation between the experimentally measured range and the range calculated using the speed as determined by the photogates. In this paper, we will discuss the origin of this systematic error and derive a simple formula to correct it. In particular, we find that the launch speed given by our instrument is significantly different from the actual launch speed of our projectile.

Using model rockets to teach physics can be an effective way to engage students in learning. In this paper, we present a curriculum developed in response to an expressed need for helping high school students review physics equations in preparation for a state-mandated exam. This required a mode of teaching that was more advanced and analytical than that offered by Estes Industries,1 but more basic than the analysis of Nelson et al.2,3 In particular, drag is neglected until the very end of the exercise, which allows the concept of conservation of energy to be shown when predicting the rocket's flight. Also, the variable mass of the rocket motor is assumed to decrease linearly during the flight (while the propulsion charge and recovery delay charge are burning) and handled simplistically by using an average mass value. These changes greatly simplify the equations needed to predict the times and heights at various stages of flight, making it more useful as a review of basic physics. Details about model rocket motors, range safety, and other supplemental information may be found online at Apogee Components4 and the National Association of Rocketry.5

Edwin Herbert Hall (1855–1938), discoverer of the Hall effect, was one of the first winners of the AAPT Oersted Medal for his contributions to the teaching of physics. While Hall's role in establishing laboratory work in high schools is widely acknowledged, his position as chair of the physics section of the Committee on College Entrance Requirements was contentious and his involvement in launching College Board Physics, what we call the “other Hall effect,” has largely been overlooked.1 This article details Hall's role in the development of College Board Physics.

This paper describes the authors' experiences transforming a “cookbook” lab into an inquiry-based investigation and the powerful effect the inquiry-oriented lab had on our students' understanding of lenses. We found the inquiry-oriented approach led to richer interactions between students as well as a deeper conceptual understanding of how images are formed. We observed engaged students participating in scientific discourse full of hypothesizing, modeling, and argumentation based on evidence.